- Text too small to read
- Content wider than screen
- Mobile viewport not set
- Links too close together
More details can be check here:https://www.google.com/webmasters/tools/mobile-friendly/?url=
- Use legible font sizes. The following text on your page renders in a way that may be difficult for some of your visitors to read. Use legible font sizes to provide a better user experience.
- Size content to viewport. The page content is too wide for the viewport, forcing the user to scroll horizontally. Size the page content to the viewport to provide a better user experience.The page content is 1,179 CSS pixels wide, but the viewport is only 980 CSS pixels wide. The following elements fall outside the viewport:
- Configure the viewport. Your page does not have a viewport specified. This causes mobile devices to render your page as it would appear on a desktop browser, scaling it down to fit on a mobile screen. Configure a viewport to allow your page to render properly on all devices.